1. Field of the Invention
This invention relates to the art of electrical resolvers, and more particularly concerns a segmented resolver having an arcuate stator and coaxial arcuate rotor.
2. Description of the Prior Art
Electrical resolvers are well known in the art and are often employed to transfer a physical quantity into an electrical quantity or vice versa. The physical quantity may be the angular rotation of a rotor with respect to a stator, and the electrical quantity may be a voltage whose amplitude and/or phase may change in coordination with changes in angular position of the rotor. Basically a resolver comprises a rotor and a stator, each having independent differently positioned windings. If an alternating input voltage is applied to the rotor winding an alternating output induced voltage will appear at the terminals of the stator winding. If the rotor is turned angularly by mechanical means such as a servomotor, the change in angular position of the rotor, expressed in degrees of arc, will cause a change in output voltage of the stator. Measurements of the output voltage change will provide an indication of the extent of change in angular position of the rotor. The resolver may be regarded as a signal transformer which has a variable ratio of output to input voltage.
Resolvers may be classified as one "speed" or multispeed (2 "speed", 8 "speed", etc), where the term "speed" corresponds to the number of pole pairs in a resolver winding.
Standard conventional electrical resolvers employ a stator and rotor both ring-shaped and mounted within coaxial sleeves or hubs to keep the stator and rotor in concentric position. In order to achieve good concentricity the mounting surfaces must have tight tolerances. Any irregularities on the mating surfaces create stresses within the resolver. These stresses increase over the operating temperature range of the resolver, since coefficients of thermal expansion for the hub/sleeves and their mating parts cannot be matched exactly within the resolver. Any stress in such a resolver causes a change in its operating characteristics. This can create an error in angular indication, change in null voltage, etc. Other objections are large sizes, heavy weights, insufficient accuracy, complexity and high costs.